Which of the following is not an electrophile?

The cyanide ion $(CN^-)$ is:

Which of the following is an ambident nucleophile?

The cyanide ion $(CN^-)$ acts as an ambident nucleophile. From which end does it act as a stronger nucleophile in an aqueous medium? Give a reason for your answer.

Which of the following cannot act as a nucleophile?

Giving justification,categorise the following molecules/ions as nucleophile or electrophile: $HS^{-}, BF_{3}, C_{2}H_{5}O^{-}, (CH_{3})_{3}N:, \overset{+}{Cl}, CH_{3}-\overset{+}{C}=O, H_{2}N:^{-}, \overset{+}{N}O_{2}$